Ventilating tubing



April 19, 1949. E. F. MAHLBERG 2,467559 VENTILATING TUBING Filed .June 19, 1945 L/lro'flMahlbeJg INVENTOR lBY- ATToRNY Patented Apr. 19, 1949 VENTILA'HNG TUBING Eiroy F. Mahlberg, Fairfield, Conn., anignor to E. I. du Pont de Nemours Company, Wilmington, Del., a corporation of Delaware Application June `19, 1945, Serial No. 800,393

(Cl. 13S-49) ZCialms. l

This invention relates to exible non-collapsi-l ble ventilating tubing particularly adapted for use in ventilating mines. tunnels, ship-holds and the like.

A number of devices and arrangements have been employed in the manufacture of ventilating tubing as reinforcing means to reduce the tendency for such tubing to collapseywhen air is drawn through it under vacuum. One such construction provides for a series of spaced metal hoops within the fabric tubing and riveted or otherwise fastened to the tubing. Anotherv arrangement provides for the Iuse of metal strips anchored between two layers of fabric and spaced at intervals of from 4 to 8 inches. These and other similar devices however are expensive, not readily portable, difficult to/pack for shipping, not readily adapted for use where sharp turns or curves are required or are not sulciently're.- sistant to collapsing under the reduced pressures encountered in producing the maximum air cir culation.

'I'his invention has as an object, the provision of a simple, inexpensive and practical Ventilating tubing, which eliminates the defects of previously lavailable tubing. Another object is the provision of an improved portable Ventilating tubing which is resistant to kinking and buckling. Another object is the provision of lightweight Ventilating tubing which may be readily compressed into a relatively small space for convenience in storage and shipping. Another object is the provision of an improved Ventilating tubing which ismore resistant to collapsing under higher vacuum and which does not reduce the passage of air when` sharp bends or turns are required in the ventilation installation. Another object is the provision of a. flexible, Ventilating tubing which may be manufactured in sections of any desired practical length and diameter so as to be readily assembled and disassembled for any required installation. A further object of the invention is the provision of an improved Ventilating tubing wherein the effective diameter of the tubing is maintained under reduced pressures, thus providing less internal friction from passage of air within the tube. Other objects will become apparent as the description of the invention proceeds.

These objects are accomplished in accordance with the present invention by means of a gas impermeable fabric tubing preferably provided with an extended longitudinal seam as a suspension means and an interiorly located helical metal coil or helix reinforcing member of diameter slightly greater than that of the fabric tubing preferably permanently joined to circular rings permanently attached to the interior wall of the fabric tubing near the ends of each section. In order to illustrate the invention, reference 101s made .to the attached drawing in which Figure 1 illustrates the position of the relaxed helical coil on a mandrel, the first step in themanufacture of the improved tubing.

F'igure 2, which represents the second step in the processing, illustrates the helical coil on the mandrel in a contracted state.

Figure 3 is a sectional view of the helical vcoil in the contracted position on the mandrel and encased within the fabric tubingcarrying a longitudinal suspension seam. v y Y,

Figure 4 is a sectional view similar to Figure 3 except that the helical coil is shown in its ,-relaxed normal diameter.

Figure 5 illustrates the nal'unitary structure with the helical coil in the relaxed normal .diameter and joined to metal rings at thefopposite terminals of the coil.

In the drawing, I is a helix or helical wire coil which serves as the reinforcing member for the fabric tubing 5 consisting of rubberized fabric or fabric otherwise treated to render it impermeable to gases. The rod or mandrel 2, fitted with a clamp 3 to hold one end of the helix in a fixed position to permit contraction of the helix when twisted. serves as a temporary sup--v port for the helix to facilitate threading ofthe flexible fabric tubing 5 over the helix. Metal rings 6 are attached interiorly to each endof the fabric tubing section and the ends of the helix are also fastened 'to these rings by welding or riveting. The suspension seam l, which forms a unitary part of the flexible fabric tubing, may be provided with suitable hooksvfor attaching to supports in any desired installation.

In manufacturing the improved Ventilating tubing. a metal wire coil or helix I with a relaxed diameter slightly greater than that of the fabric tubing 5, is slid over a mandrel 2 and attached temporarily by any convenient means 3 at onel end of the mandrel as in Figure l. The free end of the helix is then twisted as indiannuo cated inl,- Figure 2 so as to contract or reduce the diameter of the helix. While the helix is held in this contracted state, the flexible fabric tubing is threaded over the helix which is then released from the twisting pressure, thus causing the helix to expand to its normally relaxed diameter against the interior surface of the flexible fabric. The restrained terminal of the helix is released from the clamp 3 and the helix reinforced tubing removed from the mandrel. The terminals of the helix are then permanently attached to rigid metal rings 6 inserted in the tube, by 4welding or riveting and the rings also permanently attached to the fabric tubing by rivets 1. In order to permit assembly of a number of sections of the improved reinforced 'tubing in commercial installations, other rigid metal coupling rings not shown in the drawing may be aflixed at both termini of the tubingrto facilitate tight connections at the section joints.

The-fabric which forms the tubing proper may consist of any gas impermeable materialsuch as rubberized cotton duck or fabrics coated with the presentlyavailable synthetic elastomers for example, neoprene or acrylonitrile-styrene interpolymers, cellulose derivatives, or synthetic resins, for example, vinyl resins such as polyvinyl acetals and vinyl chloride-vinyl acetate copolymers.

The improved tubing may be manufactured in anyconvenient practical lengths and diameters. Thus the diameter of the helix may vary from between about 3 inches and 12 inches, the pitch from between about V1.5 inches and 3 inches and the diameter of the spring steel wire from between about .120 inch and .225 inch. One commercially acceptable structure is manufactured in sections feet in length with a diameter of 8 inches. The helical coil used in this particular product is composed of 60.-'10 carbon spring steel Wire, heat treated and annealed, with a diameter of 0.156 and a3 pitch. For other tubing of different diameters, the pitch and diameter of the wire of the reinforcing helical coil may be varied depending on the requirements of the installation.

Thirty feet of tubing of the type and dimensions just described has been found to be capable of handling a volume of 1200 cubic Vfeet of air per minute at 21/2" of water suction, an amount about 60% greater than with previously available flexibleventilating -tubingwhich due to partial collapse and sagging offered sufllcient friction to prevent free passage of air.

The accompanying drawing illustrates the attachment of the helix termini to rigid metal rings inserted within the fabric tubing. Although this arrangement is generally preferred, satisfactory results may also be obtained by riveting the helix .termini to the interior walls of the Ifabric tubing inconjunction with a small reinforcing piece, for example, a 1/2" x 2" piece of heavy leather', duck fabric or rubber. The metal gfring coupling is then placed at the extreme ends i'fpfgthe tubing as previously described preferably ,guite close (about 1/2) to the helix termini. @3e-In the ,preceding description, provision Vis made 'forfthe attachingA of the helix at the terminals .only, the remainder of the helix being unrestrained except as contained in the` fabric covering, that is the helix is free to move independently of the fabric if the structure is bent or twisted except as controlled at the terminals and within the connes of the fabric wall. However, if desired the helix in its relaxed state may also be joined to the interior wall of the fabric tubing at all points or at intermittent points by means of a 4 suitable adhesive layer on the walls of the tubing in which the helix may be embedded or by means of staples. thus further restraining movement of the helix.

The product of the invention is useful in the.

mining, ship-building. air conditioning and general ventilation fields and can be installed on a permanent basis or it can be used with portable ventilation systems.

The improved Ventilating tubing is distinguished by manyimportant advantages. It is light in weight (about half the weight of certain previously available tubing which has been employed commercially for similar purposes) and this factor combined with the ready, compressibility of the structure to about V. the normal buckling and may be employed where sharp bends and turns areI encountered, without substantially reducing the volume of air passed through the ventilation system, thus eliminating the need for special sections at these points. The construction is simple, durable and inexpensive and entirely practical Vfor all commercial ventilation systems.

It is apparent that many widely different embodiments of the invention may be made without departing from the spirit and scope thereof and therefore, it isnot intended to be limited except as indicated in the appended claims.

I claim: 1. A flexible, non-collapsible Ventilating tubing comprising a pre-formed gas impermeable fabric tubing of uniform diameter which would collapse under its own weight in the absence of internal reinforcement, a reinforcing and supporting.

member telescoped through the tubing and consisting of a light-weight, loosely-coiled metal helix having a diameter slightly greater than that of the preformed fabric tubing when fully expanded and being of suillcient strength to prevent collapse of the tubing even when the latter is subjected to suction, the coils of the helix being unobstructed internally, and means for anchoring only the ends ofthe helix to the tubing, said means comprising rigid metal rings connected to the ends of the helix and arranged wholly within the outline of the tubing but attached thereto.

2. A flexible, non-collapsible pre-formed ventilating tubing comprising a section of coated fabric formedinto a tube of uniform diameter, which would collapse underits own weight in the absence of internal reinforcement, with the longitudinal edges of the fabric joined together to make'a longitudinal seam. a reinforcing and suponly the ends of the helix to the tubing, saidy 5 6 means comprising rigid metal rings connected to Number Name Date the ends of the helix and arranged wholly within 713,560 Dodge Nov. 11, 1902 the outline of the tubing but attached thereto. 1,344,321 Urbinal June 22, 1920 1,472,518 Stillette et al. Oct. 30, 1923 ELROY F. MAHLBERG. 5 1,666,365 Bradbury Apr. 17, 1928 1 1,731,322 Riddle Oct. 15, 1929 REFERENCES CITED 1,774,983 Loughead Sept. 2, 1930 The following references are of record in the 118635624 Evans June 21 1932 me f the man 10 ejsk t i333 ov. UNITED STATES PATENTS 2,176,762 Forbes oct. 17, 1939 Number Name Date 2,396,059 Roberts Mar. 5, 1946 147,446 Stilwell Feb. 10, 1874 165.324 Greacen July 3, 1875 4 

